A "significant" discovery revolving around a fingerprint, an unidentified man, and a 2012 traffic stop in British Columbia, led a Supreme Court justice to declare a mistrial in Yellowknife on Tuesday.

William Simpson and Richard Shushack are both facing charges of possession of an estimated $500,000 worth of marijuana and cocaine for the purpose of trafficking. The charges stem from a 2014 incident where firefighters found the drugs while responding to a call to Hudson House apartments about an unattended pot on a hot stove.

Earlier in the trial, which started late last week, court heard a third print belonging to a man named Sam Bennett was found on the drugs.

What the defence didn't know until Tuesday morning was that police and the Crown knew of an earlier connection between Bennett and Simpson. Bennett was stopped by police in B.C. in 2012 while riding a motorcycle registered to Simpson.

Simpson's lawyer, Peter Harte, told Supreme Court Justice Shannon Smallwood he was panic stricken to have learned of the significant connection this late in the trial, because had he known police knew of it earlier, he would have pursued a totally different line of cross examination.

"To suggest the defence was taken by surprise doesn't adequately describe the situation," said Harte. "I was shocked, stunned."

Defence case hinged on RCMP investigation

The crux of Harte and Shushack's lawyer Kate Oja's defence has hinged on the adequacy of the RCMP's investigation.

Harte and Oja questioned why there is no evidence that police followed up on Bennett's fingerprint.

They also pressed RCMP investigators to explain why they did not attempt to identify a man who was also at the apartment the day the drugs were discovered.

Staff Sgt. Steven Burrill testified that the man acted "shocked" to see a police officer at the door of the apartment in 2014.

"His actions, to me, were very suspicious," Burrill testified last Wednesday.

Harte, Oja and Crown prosecutor Annie Piche all agreed that the apparent existence of a third person is a "live issue" in the case.

Smallwood took about 45 minutes to consider the arguments. When court reconvened, she called the lack of disclosure "troubling" and declared a mistrial.

After court was adjourned, Piche said she's known about the connection between Simpson and Bennett for a long time.

"I don't know how it happened," she said, calling the lack of disclosure an administrative error. "It needs to be investigated on our part."

They case will reconvene Monday to set a date for a new trial.